This study was initiated to understand the mechanism of re-differentiation of neoplastic cells by various chemical agents. The research is directed at present to determine: (1) The effect of dimethylsulfoxide (DMSO) and its analogs on the expression of the enzymes in the gamma-glutamyl cycle in hepatoma cell lines in culture, transplantable hepatomas as well as the Friend erythroleukemia cell line; (2) the effect of polar compounds such as DMSO, bisacetamides and antitumor agents on fetal expressions (such as alpha-fetoprotein) in hepatomas and CEA in colon tumors; (3) the reversibility, when exposed to the above-mentioned agents, of choriocarcinoma in tissue culture using HCG as marker.